This paper presents an eddy current field calculation method of additional loss in transformer based on 3D finite element analysis in order to accurately calculate and control the additional loss.The distributions of eddy current and additional loss in a transformer were calculated.In the calculation of eddy current field

the permeability and conductivity of core material were disposed to be anisotropic to equivalent to the lamination effect of core plates.In the post-processing of leakage field

the distributions of eddy current and eddy current loss were gained

and several factors that affect additional loss were studied.The result shows that additional loss can be effectively reduced by taking non-magnetic materials as structure

adjusting the distance among structures

and using the tapping type of middle wiring.Furthermore

the additional losses of various types of transformers were tested

and the calculation results agreed well with the experimental data.